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Help needed. Electrical issue. Starting/charging/dash went nuts.


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Hi, been a long times since I have needed help. But me and my 1991 Lexus LS400 are back.  Had an issue with my starter going out on me. The mechanic I used for 15 years past away so I needed to find a new one.  Found a guy who came to me. Started the job and then disappeared never to come back or return a call.  He got the new starter in, but that is were he stopped.  Found a new guy. Really good. He finished the job along with putting in all new ignition parts due to other guy messing up wires and distributors caps. The car is about 20 thousand miles away from needing that. So I put in all new stuff. Also put in new thermostat, new battery. Mechanic also cleaned intake and fuel injectors.  On working on car he discovered an issue with the wiring harness. About 2012 or 2014 I had the front passenger tire blowout. A part of the tire went through to the engine compartment and took out part of the main wiring harness by the firewall. It was fixed by insurance and had been fine.  Until now. A wire or two shorted in the repaired are. Making it so the car would not start with the key. If you by past it though the fuse box, car started etc. So he pulled the wires that had shorted (they even melted) and repaired with new.  He then took car for a long drive. Even up a very nasty locale car killing step grade. All was OK.  He also charged the battery before doing so and tested cooling system along with that the car was charging.  He drove the car to me. I drove him back to his place. On the way home my issues started.  The car stalled after I stopped at a store and started it to leave. On trying to restart car was completely dead. No clicking. No sound from starter.  I sat for about 5 to 10 minutes. And don't know why but tried it again. Car started right up. Starter sounded great and cranked fast.  On getting home and keeping the car running the headlights stopped working. They were switched on. The dash acted like they were on. But no headlights.  I turned them on and off a few times and they would not come on. But the dash lights started going nuts. Sometimes some of the indicator needles on the mph or rpm or temp or gas, etc., went out. Not all at the same time. Just different ones when I flipped the lights on and of.  Turned the car off. It would not restart. Turning the key I got nothing. No click. Nothing. Checked the battery with a smart charger. It was at 11.5 volts.  Gave up for the day. Left the smart charger on all night.  Car started perfectly in the morning. Headlights worked fine. Dash lights worked fine. Turned car on and off a few times. All good. Restarted car to take a charging reading. Got nothing engine running. No charge from alternator. Voltage had come down to 11.5 volts. I need help. Need to pick your brains. I know it could be the alternator. I know it could be the cpu that controllers the alternator.  But I never had a dash go nuts like that before..... I've had low batteries before. Needed jumps before and so on. But never the dash going nuts and no headlights when switched on. Not even dimly lit. So could it be an issue with other wires in that part if the wiring harness? I know if it is the harness it could hurt the alternator and the charging cpu.  Help please. I don't want to just throw (expensive) parts in and see what happens.  Sorry for the long post. But I know sometimes every detail and so on helps. Now you know as much as I do. Anyone ever have their dash go nuts?  As always a great big thanks to all!  I edited this to fix typos etc.

Also important forgot to mention. I'm in a rual area of Arizona. Where California, Arizona, and Nevada come together by the Colorado River. Las Vegas is the bigist nearby city at a little over 100 miles away.

Again, thanks to all.

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I would take it to an auto electrical specialist to diagnose the fault....it could be a damaged alternator from dropping an earth...e.g. losing a phase, diode's damaged, etc.

Also, the battery could be old enough to not retain a charge and therefore the alternator is not able to provide the full current required.

Check also any other wiring (especially earth points) where there could still be some damage which is undiscovered.

Otherwise, it seems that you are going in the right direction and it is now just a case of fettling the faults that remain.

Let us know how you get on with it all

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Thank you for responding. I know it is tempting to skip parts on a long post and just respond.

But this post is long becouse I wanted to give out all the needed information.

Like the part about a new battery already being put in the car. And yes, we did test it more then once.

The posability of a bad connection is one of the items we will be running down. The connections that are a easy reach at the battery have been checked with a meter for resistance.

Realy need to hear from anyone that has info on what could make the headlights/dash do what it did and how you fixed it.

Thank you.

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Check the condition of the driver's side wiring harness in the LH fender, the connections to the harnesses at the distribution/fuse/relay blocks under the hood, and where the harnesses from the engine compartment meet at the fuse/junction block under the dash (driver's side).  The harnesses that go into the under-dash distribution block plug then screw in (10mm or phillips head, like most everything on the car). I wonder if that connector's loose.

If you're digging that far into things, it would be worth your while to buy the electrical section shop manual (if you can find a used one for a reasonable price) or buy a one-day pass to Toyota/Lexus' TIS (tech info system) online, to download the pages appropriate to your situation (wiring diagrams/schematics, etc).

Good luck and please keep us updated as to what you find.

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